/*
 * Copyright (c) 2008, Ivan Appel <ivan.appel@gmail.com>
 * 
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * - Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer. 
 * - Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution. 
 *
 * Neither the name of Ivan Appel nor the names of any other jThinker
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission. 
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package oss.jthinker.util;

/**
 * Trigger that changes state along with some monitored trigger and
 * converts the ingoing values accordingly.
 * 
 * @author iappel
 * @param inT type of monitored trigger's state
 * @param outT type of this trigger's state
 */
public abstract class DerivedTrigger<inT, outT> extends Trigger<outT>
        implements TriggerListener<inT> {

    // Trigger to monitor
    private final Trigger<? extends inT> datasource;
    
    /**
     * Creates a new DerivedTrigger instance.
     * 
     * @param input trigger to monitor
     */
    public DerivedTrigger(Trigger<? extends inT> input) {
        datasource = input;
        if (datasource.hasState()) {
            this.setState(convertValue(datasource.getState()));
        }
        datasource.addStateConsumer(this);
    }
    
    /**
     * Converts the value from monitored trigger's type into
     * current one's.
     * 
     * @param value monitored trigger's type
     * 
     * @return according internal value
     */
    protected abstract outT convertValue(inT value);

    /** {@inheritDoc} */
    public void stateChanged(TriggerEvent<? extends inT> event) {
        if (event.getSource() == datasource) {
            outT newState = convertValue(event.getState());
            setState(newState);
        } else {
            throw new IllegalArgumentException(
                    "This trigger is not monitored: "+event.getSource());
        }
    }
}
